The present invention relates to a new and improved construction of a gas-blast switch.
Generally speaking, the gas-blast switch of the present development is of the type comprising two coaxially arranged contact elements which, by performing an axial movement, can be brought into and out of engagement with one another. The first contact element, which is connected with a drive, is arranged forwardly in a fixed reference position with respect to a blast nozzle. The blast nozzle is connected at its inlet side with a compression chamber or space for an extinguishing gas, this compression chamber being pressurized during the cut-off stroke of the gas-blast switch. The second contact element engages with the blast nozzle in the cut-on position of the gas-blast switch. Further, the second contact element is surrounded by a screening body or element which, by means of the blast nozzle during a cut-on stroke, can be shifted out of its position which is advanced during the cut-off position, against the action of a spring, rearwardly along the second contact element.
Such gas-blast switches are known, by way of example, from Swiss patent No. 554,597 or German patent publication No. 2,140,284. With these gas-blast switches the screening body, during a cut-off stroke, has assigned to it the function of rendering uniform the electrical field which emanates from the end of the second contact element which as a rule is of tubular-shaped configuration, in order that, following extinguishing of the switching arc, there do not exist any extreme values of the field intensity.
The spring, whose force is applied to the screening body, additionally affords the advantage that towards the end of a cut-on stroke the thus moved parts of the gas-blast switch are effectively delayed. Hence, there is also stored a part of the mechanical force which is applied during the cut-on stroke by the switch drive, by the spring until the next following cut-off stroke and such then augments the cut-off stroke.
With the heretofore known gas-blast switches the second contact element, which is operatively associated with the screening body, is stationarily arranged. As a result, the path through which moves the first contact element during a cut-off stroke must exactly correspond to the switching path which is present between the contact elements in the cut-off position. Additionally, it is a known fact that the separation path between the contact elements, i.e. the minimum distance which the contact elements must possess from one another, so that there is even realized at all an extinguishing of the switching arc, must be greater the greater the magnitude of the currents which are to be interrupted. It is of course to be strived for that the separation distance be reached as quickly as possible during a cut-off stroke. This requires that, with the state-of-the-art gas-blast switches that there be present a long stroke drive mechanism which, additionally, must have sufficient power output in order to cause the desired separation spacing or distance within a useful period of time.